The invention relates to an open-end spinning unit with a spinning rotor open on one side and having a closed bottom and closed lateral walls, the open side of which spinning rotor is covered with a closing component containing fiber supply means directed at a slide wall of the spinning rotor, a yarn take-off duct, and a suction duct.
In open-end spinning units the loosened fibers are transported to the spinning rotor with the aid of a stream of air leading from an opening roll to the spinning rotor. In order to produce the stream of air, subatmospheric pressure must be generated in the area inside of the spinning rotor.
It has been known (DOS [German Unexamined Published Application] 1,560,333) to provide the rotor walls with ventilation bores and to arrange the spinning rotor inside of a rotor housing connected to a source of subatmospheric pressure. In this structure the subatmospheric pressure prevailing in the rotor is caused by the spinning rotor itself and by an external indraft source. In this construction, the spinning rotor edge bordering the open lateral face is sealed off with a sealing gap against a fixed housing insert. This insert is then covered once again with a cap having an insert projecting into the spinning rotor. Further, there must be an additional seal at the point at which a shaft of the spinning rotor penetrates the rear wall of the rotor housing. The fact that it is not possible, prior to a piecing operation, to simply free the spinning rotor of fiber remains or the like by drawing them off by suction is unfavorable in this construction. Instead, the spinning unit must be opened so that the rotor is accessible.
It has also been known (DOS 1,710,026) to provide spinning rotors with closed lateral walls and a closed bottom, which walls and bottom are arranged in a rotor housing connected to a source of subatmospheric pressure in such a way that, proceeding from a fiber supply duct, air flows from the rotor interior by way of the edge of the open side to the rotor housing and from there flows to the suction connection. This structure then opens up the possibility of drawing off fibers or the like from the rotor interior by suction when the rotor is at a standstill. However, this construction entails the difficulty that the subatmospheric pressure prevailing in the interior chamber of the rotor and also the velocity of the air flowing over the rotor edge are dependent on the dimensions of the spinning rotor and the rotor housing, so that in practice problems arise in using rotors of different sizes on the basis of this principle.
It has likewise been known (DOS 1,710,715) to attach a suction duct directly to the rotor interior from a spinning rotor in which the spun yarn is discharged through the hollow shaft. This construction provides a structural part extending into the spinning rotor with a cylindrical hub-shaped attachment having an orifice of a fiber supply duct on its lateral face. The middle section of this structural part is formed as a suction duct with a large cross section.
Further, it has been known (DOS 2,308,707, FIG. 2) to equip a closing member for a rotor housing receiving a spinning rotor with an annular suction duct in the middle section. In this construction, a fiber supply duct terminates in the end face of the closing member in such a way that the orifice of this fiber supply duct is located radially further out than the orifice of the middle suction duct.
In another construction using this basic principle (DAS [German Published Application] 2,130,723) the spinning rotor is also arranged in a closed rotor housing. In this structure, the fiber is supplied by way of a fiber supply duct terminating inside of an annular groove formed between the end surface of a hub-like component projecting into the spinning rotor and a fiber guide shield arranged concentrically with respect to the rotor axle. A suction duct which will take in air with a high air velocity leads through said annular groove to the external face of the fiber guide shield.
A common aspect of all of the constructions in which the transport air is drawn in by suction directly from the rotor via the closing component is that the orifice of the suction duct maintains a greater spacing with respect to the interior walls of the spinning rotor than do the orifice of the fiber supply duct or the edges of the fiber guide disks. This results in the deflection of the transport air to the suction duct directly after leaving the fiber guide means, i.e. the fiber supply duct or the fiber guide shield. The danger exists that thereby a considerable portion of the transported fibers are taken in directly via the suction duct and do not reach the fiber slide surface of the spinning rotor. In all of these constructions the orifice of the yarn take-off duct is also located in very close proximity to the orifice of the suction duct, so that the piecing process is made extremely difficult. For, in order to piece a thread, a thread end must be returned via the yarn take-off duct so far into the spinning rotor that the thread end attaches to a fiber ring deposited in the spinning rotor and can be pieced. In the conventional constructions there exists the danger that the thread end is prematurely taken into the suction duct before it can reach the area of the collecting groove of the spinning rotor, so that piecing is impossible. The difficulties described are probably the reason that these structures have not entered practice.
It is an object of the invention to construct an open-end spinning unit of the type named hereinabove in such a way that the subatmospheric pressure necessary for fiber transport can be produced with uniform magnitude in the interior of the spinning rotor on all spinning units of an open-end spinning machine with a minimal energy requirement and that the fibers are transported reliably to the fiber-collecting groove of the spinning rotor without the occurrence of rather large fiber losses due to air intake and without significant complications to the piecing operation. This problem is solved in that the orifice of the suction duct is located, at least partially--in a radial direction with respect to the spinning rotor--closer to the slide wall of the spinning rotor than the fiber supply means.
This construction achieves the fact that the fibers exiting from the fiber supply means are seized by an air current having a flow component directed toward the slide wall of the spinning rotor, thus increasing the reliability that all of the fibers reach this slide wall. Once the fibers have reached the slide wall of the spinning rotor, then the frictional force between the fibers and the very rapidly rotating spinning rotor is greater than the entraining force of the air current, so that the fibers are not removed by way of the suction duct.
In an expedient preferred embodiment of the invention, it is provided that the orifice of the suction duct--in an axial direction of the spinning rotor--is located closer to the open lateral face of the spinning rotor than the fiber supplying means. This embodiment generates an axial air current inside of the spinning rotor in the direction toward the open end of the spinning rotor; this axial air current further increases the chances of the fibers of also really reaching the slide wall of the spinning rotor. In this connection, it can be seen as especially advantageous that the slide wall of the spinning rotor conically tapers toward the open end of the spinning rotor. The air flowing in the spinning rotor is also entrained in a peripheral direction by the spinning rotor, so that there results an air whorl, flowing toward the orifice of the suction duct, within which air whorl the fibers being carried forward move outwardly so that they reliably contact the slide wall of the spinning rotor.
In order to achieve to an even greater extent that the air current occurring inside of the spinning rotor is closely adapted to the interior walls of the rotor, it is advantageously provided that the suction duct--seen in the plan view of the open lateral face of the spinning rotor--extends at least nearly tangentially with respect to the spinning rotor.
In another embodiment of the invention it is provided that the orifice of the suction duct partially overlaps the edge of the open lateral face of the spinning rotor. Thus it is attained that the air current directed toward the suction duct moves very closely along the slide wall of the spinning rotor, thus further improving the depositing of the fibers.
In a further embodiment of the invention it is provided that the orifice of the suction duct is equipped with covers which adjust the orifice cross section preferably in the manner of a diaphragm. Thus the intensity of the air current inside of the spinning rotor can be influenced. According to yet further embodiments of the invention, it can also be provided that the orifice cross section is decreased for a piecing process, so that the danger can thus be likewise even further reduced that the thread end to be returned into the spinning rotor is taken into the suction duct before reaching the fiber-collecting surface of the spinning rotor.
In another embodiment of the invention it is provided that the closing component is capable of being moved away from the spinning rotor with the aid of guide elements. It is thereby possible to expose the spinning rotor for examination or maintenance or the like. In this connection, the suction duct can be connected to an exhaust air duct of the spinning unit with an elastic hose. The connection to the exhaust air duct is consequently uninterrupted. In another embodiment of the invention it is provided that the suction duct of the closing component, which former is capable of being moved with the closing component, is attached to the exhaust air duct by means of a readily detachable connection. Thus it is possible to separate the suction duct from the exhaust air duct when the closing component is removed from the area of the spinning rotor. In this case, for instance, a mobile service apparatus can then be joined to this exhaust air duct, so that the means, belonging to the machine, for producing an indraft current can be attached to the service apparatus; thus the latter does not require any indraft source of its own.
In a further embodiment of the invention it is provided that the closing component together with the edge of the open lateral face of the spinning rotor forms a sealing gap. Such a construction precludes any further enclosing of the spinning rotor, i.e. the spinning rotor can be arranged completely free and without any surrounding rotor housing. This results in advantages, especially in open-end spinning machines in which the spinning rotor is mounted in an indirect bearing above its shaft, particularly in a bearing comprised of supporting disks and an axial bearing. Since a housing is omitted, the spinning rotor can then be mounted by the supporting disks in relatively close proximity to the rotor plate. In this way, the effect of imbalances is substantially reduced. Besides, the area of the bearing is very easily accessible for service and repair work.
In order to facilitate the piecing operation, it is provided in a further embodiment of the invention that a preferably adjustable thread guide element, which partially covers the orifice of the suction duct, is arranged between the orifice of the suction duct and the yarn take-off duct. This thread guide element reliably guides the thread via the area of the orifice of the suction duct without substantially affecting the occurring air current.
Also for facilitating the piecing process and for preventing the thread end from being drawn in by suction, it is provided in another embodiment of the invention that the suction duct is equipped with means for reducing the amount of air intake. This can take place, for example, by compressing the elastic hose between the suction duct and an exhaust air duct of the spinning unit, so that the duct cross section is reduced.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.